746 



Fishery Bulletin 98(4) 



maximum visibility is not reached until so far away from 

 the aircraft. The present results have not been corrected 

 for detection bias, but Harwood et al. (1996) estimated, 

 from paired-observer data, that it would be appropriate to 

 add about 40% to correct for detection bias at the peak of 

 the sighting curve even when using bubble windows. 



The sightings curve fitted to the present data set has 

 a shoulder at 670 m, and the width of the maximum-visi- 

 bility strip, a critical determinant of the precision of the 

 survey, was small. Larsen at al. (1994, Fig. 2) noted a 

 marked drop in visibility of narwhal from the air beyond 

 823 m. In other studies, visibility of beluga whales dropped 

 off beyond about 600 m from the aircraft (Norton and Har- 

 wood 1985). and by 600 m visibility of small cetaceans was 

 less than 40% of maximum (Kingsley and Reeves 1998); 

 both these surveys were flown lower than the 457 m of the 

 present survey. 



Estimates were not been corrected for diving beluga 

 whales, but instead were conservative estimates of surface- 

 visible beluga whales. Corrections to counts of beluga 

 whales for diving have been estimated from visual records 

 of their appearance and disappearance (Brodie, 1971; Ser- 

 geant, 1973; Fraker. 1980; Gauthier, 1999), by recording 

 surface signals from attached VHF radio transmitters 

 (Frost et al., 1985), and by studying diving behavior with 

 attached pressure recorders (Martin and Smith, 1992; 

 Richard et al., 1997; Heide-Jargensen et al.. 1998; Kings- 

 ley, unpubl. data). Early studies (Brodie, 1971; Sergeant, 

 1973) were restricted to nearshore areas. Correction esti- 

 mates have ranged from adding 40% (Brodie, 1971) to 

 adding 2009( (Sergeant, 1973). A correction for eastern 

 Hudson Bay, deduced from satellite-tag data on five beluga 

 whales tagged in 1993, was about 80%, but there was 

 a wide margin of uncertainty. This value was similar to 

 values estimated for beluga whales summering in other 

 waters of the Canadian Arctic (Martin and Smith, 1992; 

 Richard et al., 1997; Heide-Jorgensen et al, 1998). 



Large sampling variability is common in beluga whale 

 surveys, the species being gregarious. Most of the error 

 variance for individual strata in the line-transect sui-vey 

 was due to uncertainty in encounter rate, especially in the 

 northern Hudson Bay stratum, where a few large groups 

 were seen on a few transects. Overall, the error coefficient 

 of variation was 23%, of which about 2/3 was due to uncer- 

 tainty in encounter rate. The jack-knife bias reduction 

 (Efron, 1982) reduced the estimate of the sui-vey expan- 

 sion factor by only V/i , from 0.583 /nmi to 0.575 /nmi. 



Acknowledgments 



This work was financially supported by the Quebec Federal 

 Fisheries Development Plan, an initiative of the Canadian 

 Department of Fisheries and Oceans. I thank the Makivik 

 Corp. for support in the organisation of the Ungava Bay 

 surveys and the coastal survey of Hudson Bay, notably 

 D.W. Doidge, who arranged the aircraft contracts for the 

 Ungava Bay survey and the coastal survey in Hudson Bay, 

 and who also made several comments on the text of the 

 present article. I thank the pilots and the observer teams 



both from the south and from the local communities. North 

 Shore Air, Air Inuit, and Bradley Air provided charter 

 aircraft, and Air Baffin made fuel available for the transect 

 survey in James and Hudson bays. 



Literature cited 



Anonymous. 



1993. Agreement between the Inuit of the Nunavut Settle- 

 ment Area and Her Majesty in Right of Canada. Depart- 

 ment of Indian and Northern Affairs and the Tungavik 

 Federation of Nunavut, Ottawa, Ontario. 

 Brodie, P. 



1971. A reconsideration of aspects of gi'owth, reproduction, 

 and behaviour of the white whale iDelphinapterus leucas) 

 with reference to the Cumberland Sound, Baffin Island, 

 population. J. Fish. Res. Board Can. 28:1309-18. 

 Brown Gladden. J. G., M. M. Ferguson, and J. W. Cla.vton. 



1997. Matriarchal genetic population structure of North 

 American beluga whales Detphinapterus leucas (Cetacea: 

 Monodontidae ). Molecular Ecology 6: 1033-1046. 

 Buckland, S. T. 



198.5. Perpendicular distance models for line transect sam- 

 pling. Biometrics 41:177-195. 

 Buckland, S. T. D. R. Anderson, K. P. Burnham, and J. L. Laake. 

 1993. Distance sampling: estimating abundance of biologi- 

 cal populations. Chapman and Hall, London, 446 p. 

 Burnham, K. P.. D. R. Anderson, and J. L. Laake. 



1980. Estimation of density from line transect sampling of 

 biological populations. Wildlife Monographs 72, 203 p. 

 Campbell, R. R. 



1993. Rare and endangered fishes and marine mammals of 

 Canada: COSEWIC Fish and Marine Mammal Subcommit- 

 tee Status Reports IX. Can. Field-Nat. 107:395-401. 

 Caron, L., and T. G. Smith. 



1990. Philopatry and site tenacity of belugas. Delphin- 

 apterus leiicaa. hunted by the Inuit at the Nastapoka estu- 

 ary eastern Hudson Bay. In Advances in research on the 

 beluga whale, Delphinapterus leucas (T. G. Smith, D. J. St 

 Aubin, and J. R. Geraci. eds.), p. 69-79. Can. Bull. Fish. 

 Aquat. Sci. 224. 

 Cochran W. G. 



1977. Sampling techniques. 3rd ed. Wiley, New York, NY, 

 428 p. 

 DFO (Department of Fisheries and Oceans). 



1996. Northern Quebec belugas 5 year management plan: 

 1996-2000. Department of Fisheries and Oceans, Quebec, 

 Que. 19 p. + Annexes. 

 Doidge, D. W. 



1990. Age- and stage-based analysis of the population 

 dynamics of beluga whales. Delphinapterus leucas. with 

 particular reference to the northern Quebec population. 

 Ph.D. diss.. Dept of Renewable Resources. Macdonald Col- 

 lege, McGill University, Ste. Anne de Bellevue, Quebec, 

 190 p. 

 Eberhardt. L. L.. and D. B. SinifT. 



1977. Population dynamics and marine mammal manage- 

 ment policies. J. Fish. Res. Board Can. 34:183-190 

 Efron, B. 



1982. The jackknife, the bootstrap and other resampling 

 plans. Conference Board for the Mathematical Sciences 

 and National .Science Foundation Regional Conference 

 Series in Applied Mathematics. Society for Industrial and 

 Applied Mathematics. Philadelphia, PA, 92 p. 



